Keyboard telegraphy



Oct. 17, 1944. 1.. M. POTTS ,3 7

I KEYBOARD TELEGRAPHY Filed April 2'7, 1942 3 Sheets-Sheet 1 FUNDA-MENTAL v a A A INVENTOR. BY LOUIS 'M. POTTS Oct. 17, 1944. o -rs2,360,579

KEYBOARD TELEGRAPHY Filed April 27, 1942 5 Sheets-Sheet 2 FIG. 6 I35IIIIIIIIIIIIIIIIIIIIIIllll 77 l z III/II FIG. ll

1 2 3 4 5 6 7 8 9 10 ll l3 l4 INVENTOR. LOUIS M. POTTS Patented Oct. 17,1944 I 2,360,579 KEYBOARD TELEGRAPHY Louis M. Potts. Evanston. Ill.,assignor to Teletype Corporation, Chicago. 111., a corporation ofDelaware Application April 27, 1942, Serial No. 440,653

19 Claims. (Cl. 178-30) The present invention relates to signalingtelegraph apparatus and more particularly to improvements in printingtelegraph systems utilizing alternating current for synchronizingapparatus between outlying and central stations.

The principal object of the present invention is to produce simpletelegraph printing devices which can be operated and controlled by asmall amount of power such as is transmissible over ordinary telephonesubscribers communication loops.

Another object of the present invention is to provide a system oftelegraph apparatus whose maintenance and manufacturing cost areappreciably low and one that may be operated at moderate speeds ofsignal transmission, and that will require a minimum of local equipmentfor maintaining signal synchronism between station equipment.

In this basic conception, the present invention proposes the use of analternating current carrier wave preferably having a fundamentalfrequency of sixty cycles as is commonly available from commercialsources and having a regulated amplitude suflicient for operatingsynchronously responsive prime movers such as synchronous wound rotaryor tuned vibrating motors. Upon this fundamental wave there issuperimposed at variable positions of a signal span full or half waveamplitude modifications which in a receiving apparatus of the systemaffect specially responsive apparatus in the performance of variousfunctions such as printing, cyclic release, etc. In the utilization ofthis form of signaling, it is proposed that station equipment beprovided ,with apparatus for automatically arresting the printing andtransmitting mechanism in a normal or zero position. From this position,and with the motor elements continuing in vibration or rotation at ameasured frequency, a release or start impulse having the form of amodified full or half wave, as preferred, initiates into rotation areceiving shaft which thereupon is adapted to describe a cycle ofoperation corresponding to a predetermined number of component waveimpulses. During this cycle of operation one or more further wavemodifications are effected upon the fundamental frequency for thepurpose of operating at printer station equipment, a print hammerresponsive to the modified wave solely, or to a stronger current, aspreferred, causing to be printed, by composition of elements, acharacter symbolic of or universally indicative of the particularcombination of modified impulses thus transmitted.

ing type wheel that is made up of character fragments. These fragmentsor character component elements may be composed in various combinationsso as to form pictorially alphabetical or numerical characterrepresentations after the manner of popular conventions or onesresembling popular conventions depending upon the number of compositionelements utilized, and the degree of artistry, accepted style, orpersonal preferance employed in the design and formulation of thecharacter elements.

For a more comprehensive understanding of the present inventionreference may be had to the accompanying drawings and to the followingdetailed specification in which like reference characters designatecorresponding parts throughout and in which,

Fig. 1 is a diagrammatic circuit illustration of a central stationequipment and representations of outlying stations equipment utilizingthe principles of the present invention;

Fig. 2 is a circuit diagram of a modified practice utilizing theprinciples of the present invention;

Fig. 3 is a fragmentary curve chart illustrating several typical signalcodes-utilizing a fourteen unit wave cycle with amplified full cyclewaves;

Fig. 4 is a rudimentary application of the present invention for use innonswitching or one way installation;

Fig. 5 is a fragmentary plan sectional view of a keyboard mechanismhaving embodied therein certain elements utilized in the presentinvention;

Fig. 6 is a side sectional view of a keyboard mechanism such as thatfeatured in Fig. 5 and taken approximately on line 66 of Fig. 7;

Fig. 7 is a transverse sectional view of a keyboard transmitterapparatus such as that shown inFigs. 5 and 6;

Fig. 8 is a transverse sectional detail view featuring the principaldrive shaft and operating mechanism of the keyboard apparatus;

Fig. 9 is a fragmentary perspective view featuring a vibrating motorassembly and principal operating shaft such'as that utilized in theaforedescribed keyboard mechanism illustrations;

Fig. is a fragmentary perspective view from another angle of thekeyboard operating 'motor and auxiliary drive mechanism: and

Fig. 11 is a development view of the type wheel periphery featuring thealphabetical and numerical character fragments or component elements.

'Referring now more particularly to the accompanying illustrations thereference character ll, Fig. 1, denotes a dotted outline of a manualexchange system comprised of a pair of commercial alternating currentsupply lines l2 and I3, a power transformer comprised of the windings l4and I5, and a pair of balancing induction control transformers l3 and I1forming part of a cord circuit in a manual system or part of a linkcircuit in an automatic system. Characters l8 and I8 designate twoillustrative outlying or subscribers stations represented by dottedrectangles of which there may be any number similarly communicating withthe central station equipment.

At each outlying station l8 or l8 there may be provided a keyboardtransmitter apparatus as well as a receiving printer, the latter forrecording both outgoing and incoming communication. At stations I8 andIS, the keyboard transmitting equipment is represented by the motorarmatures 23 and 23a which are indicated as being in series circuitconnection with the printer motor armatures 24 and 24a from a center tapof local primary transformer windings 25 and 25a whose secondarywindings 28 and 23a are in circuit with printer operating magnets 21 and21a.

The keyboard apparatus at each station is adapted to supervise a pair oftransmitting contacts 28 and 28a which lie in one of the lines 29 or 3|which form part of a pair connecting each outlying station with thecentral oilice H, the other lines of said pairs being designated 32 and33, respectively.

Outlying station I8 is connected over its line 28 to one terminal of awinding 34 at the central station transformer I! while its other line 32is connected with one terminal of a winding 35 of the other centralstation transformer is, the opposite terminals of said windings 34 and35 being connected together and joined by a line 36 from one of theterminals of the power transformer's winding l5 whose opposite terminalextends through -a filter condenser 31 to ground. In correspondencetherewith outlying station I8 is connected over its lines 3| and 33 withthe opposite windings 38 and 33 of the transformers l1 and I 8,respectively, and these windings are connected together at theiropposite terminals and also over line 38 to the winding I5 of the powertransformer as afore-described.

In accordance with this arrangement of elements, alternating currentsupplied from lines l2 and I3 induces a secondary voltage in winding l5which is carried over line 38, to the two windings 35 and 33 oftransformer l6 whereby each neutralizes the impedance eflect of theother. These secondary power current pulsations travel in the samedirection over lines 28 and 32 to the midpoint of local transformerprimary 25, it being noteworthy that because the halves of coil 25oppose each other, no current will be induced upon the transformersecondary 23 but instead the secondary pulsations from coil l5 withoutappreciable impedance loss will traverse in series the windings 24 and23 of the vibrating printer and transmitter elements to condenserfiltered ground.

Since the secondary winding ii of the power transformer is connected ina similar manner with station l8 through the afore-described circuitconnections with coils 38 and 38, no current will be induced upon thesecondary winding 28a of that station's printer magnet 21a. As a resultof the neutralizing effects of each half of the windings of localtransformer coils 28 and 25a upon the other half, no magnetic circuit isestablished on either side of these transformers; moreover, becausewinding 35 opposes winding 38 and winding 34 opp ses winding 38, thereprevails a minimum of impedance in the respective legs of these circuitsso long as the described balance is maintained. The opening of one ofthe circuit legs by reason of the separation of contact pair 23 will,however, cause current to be induced upon one of the secondary windingsas will now be described. With the opening of one of the transmittingcontact pairs,such as 28 there is not only removed one of the balancinghalves of the coil 25, permitting the other half to actuate magnet 21,but through eflectively removing from the circuit its coil 34 oftransformer H, the winding 38 is permitted to act as an impedance and toreduce the current in circuit 3|. The major portion of current fromsupply line 38 is' thereby diverted and flows over the other leg 33 ofthe parallel paths and through the winding 38. In consequence of thiseifect, and since the impedance of coil 38 reduces the current flowthrough leg 3|, current is increased through leg 33 causing the upperhalf of winding 25a to induce a voltage upon the secondary winding 28aat station I 8. The secondary windings 28 and 26a are connected tomagnets 21 and 21a.

It will be understood that the opening of contact pair 28a through theoperation of the keyboard at station l8 will have'a similar eifect uponthe printer magnet 21 of station l8.

In the detailed description which is to follow hereinafter, the precisemanner of operation of the printing and transmitting mechanisms will bedescribed in particular detail. The immediate purpose is to convey anunderstanding of methods of operation relating to-the system generallyand to the various stations apparatus for achieving and maintainingcommunication through a central omce with other similarly equippedstations. Towards this end and with the particular object ofillustrating a further modification of the system to which the presentinvention finds particular application, attention is now directed toFig. 2-wherein there is illustrated in correspondence with Fig. 1, acentral station indicated by the rectangular enclosure 43 and tworepresentative outlying stations 44 and 45. In this system alternatingcurrent originates at a source 46 at the central station and isimpressed through the primary winding 41 of a power transformer to apair of secondary windings 48 of station 44 and 43 of station 45.

Each one of the outlying stations 44 or 45 is connected with the centraloffice by means of a pair of lines 5i and 52 or ila and 52a as clearlyindicated in Fig. 2. As in the case of the preferred embodiment, Fig. 1,lines 5| and 52 form part of a loop circuit having the afore-describedpower transformer secondary winding '48 in series, together with a pairof additional transformer windings designated 53 and 54. At the outlyingstation, each loop circuit includesv a transformer primary windingconsisting of two halves designated 55 and 56 with a midpoint tapconnecting through the vibrator motor windings 51 and 58 of the printerand transmitter, re-

spectively. The corresponding several elements at station 4! aredesignated by similar reference characters having the auxiliaryreference suilix a.

windings 5i and lit oppose each other when the loop circuit tl-II isclosed and under these conditions. no current is induced upon the localstation transformer secondary 58. However, when this balanced conditionis destroyed, only winding 58 remains eflectlve whereupon a secondarycurrent is induced in winding 88 and as a result flows to print magnet62. As a consequence of the opening of contact pair 6|, current ceasesto flow in winding 53 and on this account no current is induced inwinding Ila. Therefore, at station 45, a corresponding condition obtainswhen current is cut off in winding 55a, winding Ila induces a voltageupon secondary 58a, and magnet 82a is operated. The current for thelower circuit 52 is obtained from primary winding 41 through inductionupon secondary winding 48 which is in series with winding 54a as obviousfrom Fig. 2. Current is then increased in secondary 54 by induction fromprimary 54a. Since the circuit which includes winding 48 is at this timeopen, this current drain in the power transformer is accordinglyrelieved and the current flow through the secondary winding 49 iscorrespondlngly increased. As a consequence, the current flow throughhalf-winding 56 which is in circuit with secondary winding 54 is alsoincreased causing to be induced a stronger secondary current upontransformer winding 59. The eilective circuit is traceable from groundthrough the winding 54, line 52, winding 56, to the midpoint tap of thattransformers primary, thence through the winding of the vibratingarmatures I! and 58 to ground.

At this time, no current is induced upon winding 53a by the primarywinding 53 which is in series with the secondary 48 (now open) so thataccordingly no current is available in circuit Bla of station 45. Thisdestroys the balancing or neutralizing effect of half winding 55aagainst the other half winding 56a of the local transformer primary withthe result that a secondary voltage is induced upon winding 59a causingto be operated the print magnet 62a.

From the foregoing, it will be clear that under normal conditions withstations 44 and 45 connected together for communication throughautomatic switchboard or manual cord and plug arrangement, as wellknown, alternating current from a common source may be obtainedparallelly over circuits 5| and 52, the windings 51 and 58 causing thelatter motor elements to attain a vibration frequency which correspondswith that communicated to any other station in the system. When signaltransmission is started by the opening of the contact pair 6|, then,without interrupting the vibration frequency which is thereafteravailable over but one-half of the windings 55 and 56, there is causedto be induced a further control, and that, upon the print magnet 62 soas to produce record printing both locally as well as at the remotestation.

As has alreadybeen stated, the systems of telegraph transmissiondiscussed above though specifically designed for use with vibratingmotor function control. One of the functions now to be described is thatof print hammer operation,

type actuators may be adaptable for use with any other class ofsynchronously driven motor. The principal incentive in the use of apulsating power supply source is believed to be its adaptability as aphase regulating medium and the facility with which its undulations maybe modified for the purpose of signal transmission and a performancewhich may occur one or more times during each cycle of rotation of thetype carrying wheel. In Fig. 4, a print hammer has been designated 84and indicated as an integral element of a biased armature of polarmagnet GI at a receiving station 61. At a transmitting station 88,alternating current is obtained from a frequency regulated source whichshould have exactly the same vibrating frequency as that of analternating current source at station 01 although it has been found thattwo independent sources of supply under these conditions of operationneed not be accurately phased.

The contact pair 69 is closed periodically in accordance with theoperation of the keyboard apparatus and its performance may be identicalwith that of contact pair 28 described above.

Upon. the closure of thiscontact pair a circuit 88 is completed forenergizing print magnet 85 which thereupon will actuate its armature 64causing it to strike against the type wheel at precise cyclic intervalscoinciding with the presentation of appropriate character printingfragments of its periphery. The curve representing the signaltransmitted over line 68 may resemble the fundamental curve 18 duringany of the fourteen character cycles with the intervening periodconstituted of a straight line representing zero. The instant at whicharmature 64 is driven into impingement against the type wheel maycorrespond with the first or second half cycle of each wave. This willdepend upon the particular design of magnet 65 with regards to thedirection of its winding as effecting the permanent magnet cooperatingtherewith. For some purposes, it may be preferable to design polarmagnet 65 so that the first half wave of a complete alternating currentwave will actuate its armature affording the second half wave timeinterval in which to restore the armature to its unoperated position. Inthis way, there may be avoided a condition whereby there is firstcreated an additional bias towards the unoperated position which inaddition to the normal spring bias must be overcome during the operatinghalf wave if the relay should be designed to be eflective at the secondhalf of a full wave. Tests have proved, however, that satisfactorysupervision may be had under either conditions of polarity print magnetcontrol.

The present system utilizes a fundamental alternating current frequencywave represented in Fig. 3 at 16 and designated by the legendFundamental. This recurring undulation may betransmitted indefinitelyand its effect upon a synchronous wound motor or upon a vibrating motoris to maintain in motion the station apparatus with the regularity ofthe current stabilization factor. The manner of signaling in accordancewith the herein proposed system, consists in a practice of superimposingan amplitude modification such as designated in the example curves A, B,and I, or by changing the modified waves in any other way. however, ineither case a unit cycle of operation is desi nated by a total ofsixteen divisions. These con- 'sist of fourteen signaling intervals eachinterval of which is comprised of a full alternating current wave, thatis, two half waves of opposite characteristics, and two additionalsignal intervals or component wave intervals designated Stop and Start.

As may be noted, each one of the charted minately designed in accordancewitha plan,

certain character composition fragments.

Referring now to the illustration, Fig. 11, there is indicated a typicalarrangement of character composition fragments or elements, fourteen innumber. Thus, the letter A which consists of an amplitude modulation inthe first, fourth, sixth, eleventh, and fourteenth intervals will becomposed of the fragments illustrated in the type wheel developments andthereat designated I, 4, 8, II, and I4. A composite figure made'up ofthese fragments of printing elements in the designated order willproduce a character that may be readily identified as the alphabeticalcharacter A and after the same manner alphabetical characters B, C, etc.may be composed, as may also the numerical integers from arepresentative arrangement of fragments as designated in Fig. 11. Wherethe artistic composition of a set of communication characteristicsfollowing any other pattern is desired, it is necessary but to arrangethe fragments in shape and number to suit the particular requirement.For the purpose of obtaining a simplified and yet readily discerniblealphabet, fourteen character fragments as shown here proved sufficientfor practical comprehension.

Referring now more particularly to Figs. to 10, inclusive, attention isdirected to the detailed construction of a keyboard transmitterapparatus designed for the purpose of generating amplitude modulation ormodification signals of the type portrayed graphically in Fig. 3. Thissignal generating unit is preferably housed in an enclosure consistingof a base plate 11 and a rectangular cover housing 18. The top surfaceof the enclosure housing 18 is preferably sloped at a slight angle asclearly shown in Fig. 6 and thereat provided with a face plate 18. Thespace within the enclosure housing 18 is occupied by a set of verticallymovable character or key bars 8| all of identical profile, and a rotarytransmitting apparatus the center of which is a cyclically rotatabledrive shaft I81. An oscillatory drive shaft 82 receives its motion froma vibrating armature element generally designated 88, Figs. 9 and 10,which consists of a transverse soft iron core member 84 on which issupported a pair of windings 85 connected in series.

Electrical current is supplied to the windings 85 from suitably locatedbinding posts, in the stationary part of the motor structure, which haveelectrical communication with the conductor elements 86 and 81. These inturn are bridged with other conductor terminals 88 and 88 by means ofthe pair of conductor garter springs 8| and 82, Fig. 9. When analternating current carried parallelly' over conductors 86 and 81 isimpressed upon the windings 85 of armature 83, its pole faces, becomingalternately and oppositely charged at the current changing free repelledfrom the field magnet pole pieces 88 and 84 of a horseshoe permanentmagnet 85.

As a result, an oscillatory movement initiating with the vibratingarmature 88 is communicated through shaft 82 to a crank pin 88. Also, toreduce the amount of energy required in the operation or propulsionof.shaft 82, and to assist in maintaining regularity of time in theaforedescribed oscillatory movement, a tuned reed having the shape of acoil spring 81 is provided, one end of which is secured to a crank pindisc 88 and the other end of which is disposed in a recess 88 of aJournal plate I8I. Within the afore-mentioned recess 88, tuned coilspring 81 is anchored by mean of a variably positionable anchor lug I82through the use of which an adjustable number of coils and fractions ofcoils may be disposed so as to be free to vibrate to correspondaccurately with the current oscillations. When alternating current isapplied to a device of this sort, the first impulse, being of onepolarity, biases the armature and places a, small torsion upon thespring in one direction. As the current is reversed this torsion isremoved, the force built up in the spring is spent in moving thearmature in the opposite direction, and together with the followingreverse impulse the armature is moved further in the reverse directionthan in the direction it had attained in the first movement and therebystill more energy is stored in the spring. The accumulation of energyand accordingly the increase in amplitude continues until a condition isreached when the energy loss in each swing equals the energy added ineach swing when a constant amplitude obtains. While a certain amount ofcurrent is consumed in maintaining or in regaining this maximumamplitude of vibration, it is notably of smaller degree than that whichwould be otherwise required for performing the necessary printeroperations if no advantage was taken of the practice of storing energyfrom idle oscillations.

As best indicated in Fig. 9, the motor structure is supported as aseparate unit from the remaining portion of the keyboard apparatus andas shown in Fig. '7, may be mounted upon a pair of sidewalls I83 andI84. The crank pin 86 extends through an opening in wall I83, Fig. 5,and is received within a slot I85 of a pallet arm I86 carried freelyupon the principal operating shaft I81 which traverses longitudinallythe chamber of the housing containing the keyboard mechanism and aseries of peripherally notched operating discs I88.

In accordance with the design of driving arm I86, any variation in theamplitude or angle of rotation of motor shaft 82 is not transmittedthereto because of the fact that crank pin 96 after imparting apredetermined degree of rotation to arm I86 by reason of its engagementwith quency, do accordingly become attracted to and 7 the adjacentsurface of slot I85 will, due to overtravel, leave the slot in eitherdirection as permitted by the flared or undercut surfaces I88 which havesumcient width to accommodate all of the possible overtravel that saidpin 86 may have within the known limits of operation. Upon its 'returnmovement ,after having achieved any degree of overtravel, pin 86 followsback into the slot I85 and reverses the direction of rotation of arm I88from it previous direction repeating this phenomenon indefinitelyregardless, as has been said, of the angle of vibration or oscillation.4

While arm I86 is freely rotatable on shaft I81 asggme 5 as is also itsadjacent ratchet wheel I I I, driving connection is established .betweensaid elements I05 and III (which are integral with each other) and theshaft I01 by means of an engagement pawl I I2 pivotally carried at II4between an arm II 3 integral with shaft I01. and pallet arm I03 which issprin urged in a counterclockwise direction about its pivot II4 so as toseek engagement between its shoulder tooth II5, Fig. 8, and the teeth ofratchet wheel III successively, as the latter member is oscillatedthrough its integral association with pallet arm I05.

Thus shaft I01 is able to rotate by intermittent single step movementsas ratchet wheel III is oscillated to and fro since the shoulderedextremity II5 engages successive teeth and releases previously engagedteeth as detent I holds wheel IIIv against following backwardly, inaccordance with the conventional operation of spring urged ratchetpawls. A zero position is achieved by shaft I01 when the tail end ofpawl II2 comes into engagement with the uppermost extremity II of anauxiliary lever pivoted at II1 alongside of its associated control lever8, also pivoted at II1, see especially Fig. 8. Moreover, lever H5 isspring urged in a clockwise direction, Fig. 10, about pivot II1 untilits lowenmost extremity (plot visible in Fig. but dotted in Fig. 8)engages a liorizontally'extending shelf II9 of its control lever II8. Itis to be understood that a torsion spring I20 carried on shaft 1 whichthus urges lever II6 clockwise, Fig. 8 until its tail engages shelf II3of lever H8 is slightly stronger than the spring (not shown) whichserves pawl II2 so as to overcome the latter member upon theafore-described encounter and to coerce the pawl into a withdrawncondition and to so retain it thereafter that its shoulder H5 is unableto further engage the teeth of ratchet wheel III. Resumption ofengagement between pawl H2 and ratchet wheel III is eii'ected bywithdrawing the obstructing auxiliary lever H5 and this is done byrocking its control lever H8 in a counterclockwise direction'about pivotII1 as will now be described.

A three armed lever I2I is pivoted at I22, Fig. 8, and urged in aclockwise direction by its associated spring I23. An extremity I24 ofone of its arms follows the periphery of a cam I25 which i integrallyassociated with shaft I01.

Another one of the arms of lever I2I is provided with a hooked extremityI26 for engaging a latchable bail I21 for a purpose later to bedescribed. The third arm of lever I2I terminates with a sidewardlyextending lug or shelf I20 which is disposed in the path of one arm I29of a latch lever also pivoted at I22 and urged by a spring I3I in acounterclockwise direction so that its latching tooth I32 may engage andhold a sidewardly extending projection I33 which is integrally-formedupon one arm of the aforedescribed control lever II8 which is influencedby a spring I34 in a counterclockwise direction about pivot II1.

When thus latched through its lug I I9, control lever II8 permitsauxiliary lever IIS to be disposed sufliciently clockwise so that itssidewardly protruding lobe may engage the rearmost end of pawl II2 firstcamming and then retaining the latter members tooth I I5 out ofengagement with ratchet wheel III. As a result of this condition ratchetwheel III when reciprocated by its integrally associated arm I05 willnot cause the step-by-step advancement of shaft I01, but instead willos'cillate idly. The placing of control lever IILinto' the positionwhere it may be latched in the condition shown in Fig. 8 does not permitpawl II2 to extend its engagement nose II5 into the path of ratchetwheel III. Thereafter, reciprocating crank pin 95 moves idly, its forceterminating with the to and fro movement of the integral assembly I00-III until said control lever II8 releases pawl H2. The supervision ofcontrol lever H8 is dependent upon latch lever I29 which in turn isactuated by the three armed lever I2I. Movement of lever I2I in acounterclockwise (latch I29 freeing) direction is contingent upon areciprocation of the key bar latch bail I21 which will now be described.I

Having particular reference to Figs. 6 and 'I, it will be noted thateach key bar I35 is supported for vertical parallel movement within aslotted longitudinal guide bar I36, and a common'transverse alignmentrod I31. The several bars I35 are preferably of similar contour thoughthe location of the individual key top sections I30 and the space keyI40 is different. In this way the standard practice and arrangement of aconventional keyboard is made possible. Each key bar I35 is providedwith a sidewardly extending arm I39 which, in turn, is bent sidewardlyas at HI and is thereat engageable with- 0 in a slot I42 of anindividually associated disc I03.

Accordingly, there is provided one notched disc I08 for each key bar I35and also a return spring I43 for seeking to maintain each key bar in itsuppermost position and at the same time maintaining its associated discI08 in its counterclockwise extreme position. When one of the key topsI33 is depressed, its associated key bar I35 is driven downwardlycompressing spring I43 and rotating disc I08 in a clockwise direction(Fig. 6) through a limited angle of rotation. As a particular key barI35 is depressed, it engages universal rod I41 which rocks latch bailI21 into an extreme clockwise position, Fig. 6, entering a notch I20 oftheparticular bar I35 then operated, and the notches I30 of theremaining unoperated key bars I35 with whose level the operated key barnotches I 20 then come into horizontal registration. In this way, theoperated key is held down while the other keys are prevented from beingactuated until restoration of the former is effected.

The periphery of each disc I08 is provided with a plurality of evenlyspaced notches according to the number of component intervals of acomplete printing cycle, in the instant embodiment sixteen. Since it isdesired that the depression of each key top I38 results in thetransmission of certain ones only of the fourteen possible amplitudemodulation signals, means are provided whereby in accordance with therotation of each key bar certain preconditioning opera- I i eraldistribution of a set of longitudinal rods I44, fourteen in number. Thecontrol over the start impulse is invariable and hence for thegeneration ofthis impulse, an inert projection is provided taking theposition of one of the projections I52 when shifted or'extended. Theconnection between each disc I08 and the rods I44 and I45 is efiectedthrough the medium of the character A disc I08 with the rods I44 and I45relating to the afore-recited particular impulse waves.

A further result of the depression of any one of the key bars I35 isefiected through its enm, eii'ects die. camming of said memberrightwardly, FlgJ'l, against the compression of its associated springI5I. As a result, the remote extremity I52 of said member I48 isdisplaced from a normal extent of progusion to a somewhat greater extentwhich is suflicient to come into thejpath of a rotatable extremity I53of a contact closing lever whose other portion lies at I54 in the axialcenter of shaft I01 and the assembly of code discs I08.

Contact closing lever I53I5 4 is pivotally carried upon an endmostsupporting member or collar I55 so that when extremity I53 engages oneor morev of the displaced extremities I52 of the members I49, the lobeI54 of the contact closing lever will force contactor I58 intoengagement with one of its associated contact springs I51 depending,upon whether open or closed line is the normal line condition, and causeto be generated correspondingly signal impulse modulations asafore-described, at characteristic intervals in the gagement with theuniversal rod I41 which is integrally associated with and parallel tothe universal latch bail I21 mentioned above. Latch bail I21 is pivotedat its extremities upon the alignment rod I 31 and, upon the engagementof any one of the bars I35 with its longitudinal universal rod I41, thismember is rocked in a clockwise direction, Fig. 6 (counterclockwise,Fig.

- 8), about its pivot I31 until the longitudinal bar portion I21 engagesbehind the shouldered extremity I26 of the three armed lever I 2|. Uponthis encounter, spring I23 is overcome and three armed lever I2I isrotated slightly in a counterclockwise direction until the latchprojection I28 is securely seated behind bar I21. This holds bar I21 andconsequently the universal'rod I41 in the latched position until towardsthe end of a transmitting cycle release is eil'ected when the cycle ofrotation of shaft I01 which modulations relate at a remote station withassociated character elements, Fig. 11, of a type wheel such as thatexplained and described in copending application Serial No. 465,333,filed Nov. 12, 1942.

Contact elements I 51 and I56 correspond to the contact pair 28 in theforegoing description in connection with Figs. 1 and 2, and the openingof the circuit controlled by this contact pair results in thetransmission of a corresponding number of cam I25 engages with its camprojection the extremity I24 of three armed lever I2I.

Cam I25 being carried by shaft I01 rotates in a step-by-step manner in aclockwise direction as viewed in Figs. 8 and 10 until its cam projectionengages extremity I24 causing lever I2I to be moved in acounterclockwise direction about its pivot I22 and against the influenceof its return spring I23 until the key latching bail I21 is released andpermitted under the influence of a particular key bar spring I43, thenunder compression, to resume its normal position as designated in Fig.6. 1

Each rod I44 may have any number of paddle arms I48 connecting it withones of the discs I08 depending upon the number of times that aparticular character fragment, Fig. 11, characteristically associatedwith said rod I44 occurs in the alphabet. In other words, while certainones of the character fragments or elements, Fig. 11, may enter intocombination with other ones to make complete character symbols lessfrequently, certain others of said character elements may enter intocombinations more frequently. Ac-

cordingly, the number of paddle wheels I re-' line breaks. Concelvablyin accordance with other circuit arrangements, the normal condition ofcontact pair 28 may be open with the balance arrangements of circuitcontrol such that upon the closure of contact pair 28, a supervisoryimpulse may be transmitted to effect printing control at local as wellas outlying stations. Accordingly, in the illustration, Fig. 7,contactor I58 is designated as operable between a pair of associatedcontact points, opening at one and closing with the other in response tothe encounter of the seeker lever I53I54 with any one of the protrudingprojections I52.

There has been accordingly explained and described a system of keyboardcontrol for generating signal impulses that may be utilized in thesupervision and operation of printing telegraph apparatus in whichcommercially available and regulated alternating current is ultilizedfor maintaining synchronism, supplying the operating voltage to themotor actuating elements, as well as for supporting the signal impulsecomponents whereby intelligence is transmitted.

While the present invention has been explained and described incontemplation of certain specific embodiments, it is to be understood,nevertheless, that certain modifications and variations may beincorporated without departing from the essential spirit or scopethereof. Accordingly, it is not intended to be limited by the specificlanguage of the foregoing detailed specification nor by the particularsof the accompanying illustrations except as indicated in the hereuntoappended claims.

What is claimed is:

1. In a system of telegraphic signaling, a

source of continuous alternating current, an osaseasvo ones of ensuingcycles of a series following said coupling according to each signaltransmitted, and means to uncouple said mechanism from said motorelement after the lapse of a predetermined number of said cyclesfollowing said first cycle. y

2. In a telegraphic signaling system, a motor element continuouslyresponsive to an altemating current of constant frequency, telegraphapparatus operated by said motor including means to generate aninitiating modulation in said current and means to generate subsequentmodulations therein within a signal span, and mechanism to disconnectsaid motor element from said apparatus after the transition of apredetermined number of alternating current cycles.

3. In a signaling system, apparatus for generating an alternatingcurrent of fundamental amplitude, a keyboard apparatus, means responsiveto each keyboard operation for modifying any one of the consecutivecycles of -altemating current indicative of a startinterval therebyestablishing the beginning of a predetermined span of waves, and'meansfor modifying any one or more of succeeding cycla within said span inaccordance with fractional sign elements to be integrated into a legiblecharacter,

4. 'In a keyboard transmitting apparatus, an alternating current powersource, a transmitter shaft, a clutch for imparting cycles of rotationfrom said source to said shaft, a series of code discs carried on saidshaft, each disc representing a complete character, a plurality oflongitudinal rods peripherally arranged about said code discs, each rodallotted to a fractional sign element of a complete character, a set ofkeys each representing'a complete character, means responsive to theoperation of said keys and effective through said code discs for causingto be displaced ones of said rods for composing its complete character,and a rotary element carried by said shaft for generating impulses inaccordance with the displacement of said longitudinal rods and thefractional sign elements allotted thereto.

5. In a telegraph signaling system, a transmitting station, means forsupplying a constant frequency carrier current, apparatus at saidstation including keyboard transmitting and record printing mechanismshaving elements tuned to the frequency of said carrier current, meansassociated with said transmitting mechanism for impressing an amplitudemodulation upon any one of the consecutive cycles of said frequencycarrier current thereby establishing the beginning of a predeterminedsignal span of waves, and means for modulating any one or moresucceeding cycles within said span in accordance with fractional signelements to be integrated into a legible character. 7

6. A telegraph transmitter comprising, a set of transmitting contacts, astep-by-step motor, a rotary member advanced by said motor in cycles ofrotation having means for actuating said contacts, a series of settabledevices corresponding in number to the steps of said member during eachcycle for causing said means to actuate said contacts a number of timesand at intervals corresponding to ones of said devices, and keyboardcontrolled apparatus for characteristically setting said devices so asto thereby establish signal characteristics of an intelligencecharacter.

7. In a telegraph transmitting apparatus, a set of transmittingcontacts, a cyclically operative signal composing member comprisingmeans for operating said contacts a variable number of times duringcycle, a series or settable devices for determining the number of timesand the positions in a cycle that said member is to operate saidcontacts to generate a composing signal, vibratory means responsive toan alternating current supply for actuating said rotary member, andkeyboard controlled apparatus for characteristically setting saiddevices.

8. In a system of signaling in which intelligence symbols are analyzedinto component fragments and each fragment is allotted an individualinterval in a signal cycle, a set of control keys each related to anintelligence symbol, a series of contact controllers, a motor whose rateof speed is controlled by a constant frequency alternating current, andmeans responsive to the operation of any key of saidset of control keysfor causing to be impressed a characteristic modulation upon a variablenumber of alternating current undulations in correspondence to saidallotted symbol component fragments.

9. In a system of signaling in which each signal is comprised of anumber of component elements and each element is allotted an individualinterval in a signal cycle, a set of control keys each related to asignal, a series of contact controllers, a motor responsive to normalalternating current undulations, and means responsive to the operationof any key of said set of keys for causing to. be imposed acharacteristic modulation upon a variable number of alternating currentundulations.

10. In a signal transmission system, a plurality of character keys, aset of transmitter contacts,-

a signal generating apparatus comprising a rotary mechanism forsupervising the operation of said set of contacts according to controlby said character keys to open and close a variable number of timesduring each cycle of rotation of said rotary mechanism, means responsiveto an alternating current supply for imparting constant speed rotationto said mechanism, and means responsive to the operation of saidkeyboard apparatus and said rotary mechanism supervised contacts forproducing modulations of amplitude upon said alternating current supplyin accordance with the operation of one of said character keys.

11. In a telegraph transmitting apparatus, a cyclically operative membercomprising vibratory means for operating a set of transmitting contactsa variable number of times during each cycle, a series of settabledevices for determining the number of times during a cycle that saidmember operates said contacts, means responsive to an alternatingcurrent supply for actuating said cyclically operative member insynchronism with a corresponding member at a remote station, andkeyboard controlled apparatus for characteristically setting saiddevices.

12. In a signal transmission system, a keyboard apparatus including aplurality of character keys, cyclically operative apparatus forsupervising the operation of a set of contacts whereby to open and'closesaid contacts characteristically a number of times during each cycle ofrotation of said apparatus, means responsive to an alternating currentfor imparting regular rotation to said cyclic apparatus, and meansresponsive to the operation of said keyboard apparatus for producingselective and characteristic modulations upon said alternating current,

13. A method of telegraphic signaling which includes the procedure oftransmitting a continuous alternating current over a line definingsignalintervals by modifying at random an al ternating current cycle, andthereafter modifying one or more additional cycles of said. alternatingcurrent within a signal interval constituting a character.

14. The method of signaling which includes the steps of transmittingcontinuously over a line an alternating current of fundamentalamplitude, modifying any one of the consecutive cycles of alternatingcurrent waves by changing its amplitude and thereby'establishing thebeginning of a signal span of waves, modifying any one or more ofsucceeding cycles within said span in accordance with a signalpattern,'and terminating the signal after the lapse of a predeterminednumber of current waves with a final cycle of either fundamental ormodified amplitude.

15. In combination with a telegraph signaling apparatus, a shaft havingcyclic rotation, an oscillator for imparting rotation to said shaftcomprising a vibrator element having a predetermined tuned frequency, amagnetic coil, and means including said oscillator responsive to analternating current of a frequency identical with that of said vibratorelement when induced upon said magnetic coil for intermittentlyadvancing said shaft through its cycle of rotation.

16. In a telegraph system, a character signal shaft having cyclicrotation, a pawl-and-ratchet mechanism for advancing said shaft onetoothstep distance at a time, a driver shaft including a crank pin forengaging during a limited angle of oscillation a slot in saidpawl-and-ratchet mechanism to impelsaid pawl and for escaping andoverrunning said slot during movements of oscillation exceeding saidlimited angle of oscillation, a regulated period vibrator for impartingav fundamental frequency to said driver shaft, and a magnetic coilresponsive to alternating current fluctuations of the frequency of saidvibrator for supplementing amplitude losses of said vibrator.

17. In a signaling telegraph apparatus, means for issuing over a signalchannel a regulated frequency alternating current wave, a shaft havingsignal cyclic rotation, a pendulum for impelling said shaft byintermittent movements-coincident with each alternating current cycle,and electromagnetic means responding to said alternating current wavefor maintaining said pendulum at a minimum amplitude of vibration.

- 18.- In a printing telegraph transmitter, transmittingmans, means foractuating said transmitting means including a vibrating element hav--ing a natural oscillating frequency corresponding to that of apredetermined source of altematins current, manual control means forcausing said transmitting means to superimpose signal defining wavemodulations upon said alternating current, and means for superimposingsignal characteristic modulations upon said alternating current inpositions intervening said signal defining wave modulations.

19. In a signaling apparatus, a keyboard, means responsive to eachoperation of said keyboard and phased with an alternating current supplyfor superimposing characteristic amplitude modulations upon saidalternating current corresponding to the particular keyboard operation,and means for superimposing signal boundary modulation upon saidcurrent.

LOUIS M. POTTS.

